Fuels compositions for direct injection gasoline engines containing manganese compounds

ABSTRACT

Deposits and soot formation in a direct injection gasoline engine are reduced by providing as fuel for the operation of said direct injection engine a fuel composition comprising a fuel-soluble cyclopentadienyl manganese tricarbonyl compound.

FIELD OF THE INVENTION

[0001] The present invention relates to new spark-ignition fuelcompositions and methods for controlling, i.e. reducing or eliminating,deposits and reducing soot formation in direct injection gasoline (DIG)engines. More particularly, the invention relates to fuel compositionscomprising a spark-ignition fuel and a manganese compound and the use ofsaid fuel compositions in DIG engines.

BACKGROUND OF THE INVENTION

[0002] Over the years considerable work has been devoted to additivesfor controlling (preventing or reducing) deposit formation in the fuelinduction systems of spark-ignition internal combustion engines. Inparticular, additives that can effectively control fuel injectordeposits, intake valve deposits and combustion chamber depositsrepresent the focal point of considerable research activities in thefield and despite these efforts, further improvements are desired.

[0003] Direct injection gasoline (DIG) technology is currently on asteep developmental curve because of its high potential for improvedfuel economy and power. Environmentally, the fuel economy benefitstranslate directly into lower carbon dioxide emissions, a greenhouse gasthat is contributing to global warming.

[0004] Conventional multi-port injection (MPI) engines form ahomogeneous pre-mixture of gasoline and air by injecting gasoline intothe intake port, while a direct injection gasoline engine injectsgasoline directly into the combustion chamber like a diesel engine sothat it becomes possible to form a stratified fuel mixture which is richin the neighborhood of the spark plug but highly lean in the entirecombustion chamber. Due to the formation of such a stratified fuelmixture, combustion with the overall highly lean mixture can beachieved, leading to an improvement in fuel consumption approaching thatof a diesel engine.

[0005] However, direct injection gasoline engines can encounter problemsdifferent from those of the conventional engines due to the directinjection of gasoline into the combustion chamber. One of these problemsis related to the smoke exhausted mainly from the part of the mixture inwhich the gasoline is excessively rich, upon the stratified combustion.The amount of soot produced is greater than that of a conventional MPIengine, thus a greater amount of soot can enter the lubricating oilthrough combustion gas blow by.

[0006] There are a number of technical issues to be resolved with DIGtechnology, and one of them is injector performance with differentgasoline fuels on the world market. Being located in the combustionchamber, DIG injectors are exposed to a much harsher environment thanconventional engines with port fuel injectors (PFI). This more severeenvironment can accelerate fuel degradation and oxidation to formdeposits.

[0007] DIG technology promises about a third less carbon dioxideemissions than comparable conventional multi-port injection. This isachieved with a 10-15% improvement in fuel consumption when operating inthe homogeneous mode, and up to 35% when operating in the leanstratified mode. Fuel economy benefits also translate into fossil energyconservation and savings for the consumer. In addition, the DIGoperation platform facilitates up to a 10% power increase for the samefuel burned in the equivalent MPI configuration.

[0008] Current generation DIG technologies have experienced depositproblems. Areas of concern are fuel rails, injectors, combustion chamber(CCD), crankcase soot loadings, and intake valves (IVD). Deposits in theintake manifold come in through the PCV valve and exhaust gasrecirculation (EGR). Since there is no liquid fuel wetting the back ofthe intake valves, these deposits build up quite quickly.

[0009] Injector deposits in DIG engines restrict fuel flow and alterspray characteristics of the injectors. Low levels of fuel flowrestriction can be compensated for by engine control electronics.However, high levels of flow restriction and any level of spraydistortion cannot be adequately controlled electronically. In PFIengines, the cut-off point, as defined by the U.S. EnvironmentalProtection Agency, for injector flow restriction is 5% for any oneinjector when tested in accordance with ASTM D 5598-94. This is becausespray distortion is not much of an issue. In DIG engines, on the otherhand, charge flow characteristics in the cylinder are critical to thecalibrations that go into driveability, fuel economy, and emissions.In-cylinder charge motion in DIG engines is very sensitive to injectorspray distortion. For this reason, DIG injector flow restriction cut-offpoint may be much lower than the 5% level assigned to PFI injectorperformance.

[0010] Fuel related deposits in direct injection gasoline (DIG) enginesare an issue of current interest since this technology is now commercialin Japan and Europe. Fuel injector performance is at the forefront ofthis issue because the DIG combustion system relies heavily on fuelspray consistency to realize its advantages in fuel economy and power,and to minimize exhaust emissions. A consistent spray pattern enablesmore precise electronic control of the combustion event and the exhaustafter-treatment system.

[0011] There are numerous references teaching fuel compositionscontaining manganese compounds, for example, U.S. Pat. Nos. 5,551,957;5,679,116; and 5,944,858. However, none of these references teach theuse of fuel compositions containing manganese compounds in directinjection gasoline engines or the impact manganese compounds have ondeposits in these engines.

SUMMARY OF THE INVENTION

[0012] The present invention is directed to a fuel compositioncomprising (a) a spark-ignition internal combustion fuel; and (b) acyclopentadienyl manganese tricarbonyl compound. Further, this inventionis directed to methods of controlling deposits and reducing sootformation in direct injection gasoline engines.

DETAILED DESCRIPTION OF THE INVENTION

[0013] Cyclopentadienyl Manganese Tricarbonyl Compounds

[0014] Cyclopentadienyl manganese tricarbonyl compounds which can beused in the practice of this invention include cyclopentadienylmanganese tricarbonyl, methylcyclopentadienyl manganese tricarbonyl,dimethylcyclopentadienyl manganese tricarbonyl,trimethylcyclopentadienyl manganese tricarbonyl,tetramethylcyclopentadienyl manganese tricarbonyl,pentamethylcyclopentadienyl manganese tricarbonyl, ethylcyclopentadienylmanganese tricarbonyl, diethylcyclopentadienyl manganese tricarbonyl,propylcyclopentadienyl manganese tricarbonyl, isopropylcyclopentadienylmanganese tricarbonyl, tert-butylcyclopentadienyl manganese tricarbonyl,octylcyclopentadienyl manganese tricarbonyl, dodecylcyclopentadienylmanganese tricarbonyl, ethylmethylcyclopentadienyl manganesetricarbonyl, indenyl manganese tricarbonyl, and the like, includingmixtures of two or more such compounds. Preferred are thecyclopentadienyl manganese tricarbonyls which are liquid at roomtemperature such as methylcyclopentadienylmanganesetricarbonyl,ethylcyclopentadienyl manganese tricarbonyl, liquid mixtures ofcyclopentadienyl manganese tricarbonyl and methylcyclopentadienylmanganese tricarbonyl, mixtures of methylcyclopentadienyl manganesetricarbonyl and ethylcyclopentadienyl manganese tricarbonyl, etc.Preparation of such compounds is described in the literature, forexample, U.S. Pat. No. 2,818,417, the disclosure of which isincorporated herein in its entirety.

[0015] When formulating the fuel compositions of this invention, thecyclopentadienyl manganese tricarbonyl compounds are employed in amountssufficient to reduce or inhibit deposit and/or soot formation in adirect injection gasoline engine. Thus the fuels will contain minoramounts of the cyclopentadienyl manganese tricarbonyl compounds thatcontrol, eliminate or reduce, formation of engine deposits, especiallyinjector deposits and/or control soot formation. Generally speaking thefuels of the invention will contain an amount of the cyclopentadienylmanganese tricarbonyl compound sufficient to provide from about 0.0078to about 0.25 gram of manganese per gallon of fuel, and preferably fromabout 0.0156 to about 0.125 gram of manganese per gallon.

[0016] The fuel compositions of the present invention may containsupplemental additives in addition to the manganese compounds describedabove. Said supplemental additives include dispersants/detergents,antioxidants, carrier fluids, metal deactivators, dyes, markers,corrosion inhibitors, biocides, antistatic additives, drag reducingagents, demulsifiers, dehazers, anti-icing additives, antiknockadditives, anti-valve-seat recession additives, lubricity additives andcombustion improvers.

[0017] The fuel compositions of the present invention may, and typicallydo, contain amine detergents. Suitable amine detergents for use in thepresent invention include hydrocarbyl succinic anhydride derivatives,Mannich condensation products, hydrocarbyl amines and polyetheramines.When used, the amine detergents are typically present in an amount offrom 5 to 100 pounds by weight of additive per thousand barrels byvolume of fuel.

[0018] The hydrocarbyl-substituted succinic anhydride derivativessuitable for use in the present invention include hydrocarbylsuccinimides, succinamides, succinimide-amides and succinimide-esters.The hydrocarbyl-substituted succinic anhydride derivatives are typicallyprepared by reacting a hydrocarbyl-substituted succinic acylating agentwith a polyamine.

[0019] The hydrocarbyl-substituted succinic acylating agents include thehydrocarbyl-substituted succinic acids, the hydrocarbyl-substitutedsuccinic anhydrides, the hydrocarbyl-substituted succinic acid halides(especially the acid fluorides and acid chlorides), and the esters ofthe hydrocarbyl-substituted succinic acids and lower alcohols (e.g.,those containing up to 7 carbon atoms), that is, hydrocarbyl-substitutedcompounds which can function as carboxylic acylating agents. Of thesecompounds, the hydrocarbyl-substituted succinic acids and thehydrocarbyl-substituted succinic anhydrides and mixtures of such acidsand anhydrides are generally preferred, the hydrocarbyl-substitutedsuccinic anhydrides being particularly preferred.

[0020] The acylating agent for producing the detergent is preferablymade by reacting a polyolefin of appropriate molecular weight (with orwithout chlorine) with maleic anhydride. However, similar carboxylicreactants can be employed such as maleic acid, fumaric acid, malic acid,tartaric acid, itaconic acid, itaconic anhydride, citraconic acid,citraconic anhydride, mesaconic acid, ethylmaleic anhydride,dimethylmaleic anhydride, ethylmaleic acid, dimethylmaleic acid,hexylmaleic acid, and the like, including the corresponding acid halidesand lower aliphatic esters.

[0021] For example, hydrocarbyl-substituted succinic anhydrides may beprepared by the thermal reaction of a polyolefin and maleic anhydride,as described, for example in U.S. Pat. Nos. 3,361,673 and 3,676,089.Alternatively, the substituted succinic anhydrides can be prepared bythe react on of chlorinated polyolefins with maleic anhydride, asdescribed, for example, in U.S. Pat. No. 3,172,892. A further discussionof hydrocarbyl-substituted succinic anhydrides can be found, forexample, in U.S. Pat. Nos. 4,234,435; 5,620,486 and 5,393,309.

[0022] The mole ratio of maleic anhydride to olefin can vary widely. Itmay vary, for example, from 5:1 to 1:5, a more preferred range is 3:1 to1:3, preferably the maleic anhydride is used in stoichiometric excess,e.g. 1.1-5 moles maleic anhydride per mole of olefin. The unreactedmaleic anhydride can be vaporized from the resultant reaction mixture.

[0023] Polyalkenyl succinic anhydrides may be converted to polyalkylsuccinic anhydrides by using conventional reducing conditions such ascatalytic hydrogenation. For catalytic hydrogenation, a preferredcatalyst is palladium on carbon. Likewise, polyalkenyl succinimides maybe converted to polyalkyl succinimides using similar reducingconditions.

[0024] The hydrocarbyl substituent on the succinic anhydrides employedin the invention is generally derived from polyolefins that are polymersor copolymers of mono-olefins, particularly 1-mono-olefins, such asethylene, propylene, butylene, and the like. Preferably, the mono-olefinemployed will have 2 to about 24 carbon atoms, and more preferably,about 3 to 12 carbon atoms. More preferred mono-olefins includepropylene, butylene, particularly isobutylene, 1-octene and 1-decene.Polyolefins prepared from such mono-olefins include polypropylene,polybutene, polyisobutene, and the polyalphaolefins produced from1-octene and 1-decene.

[0025] A particularly preferred polyalkyl or polyalkenyl substituent isone derived from polyisobutene. Suitable polyisobutenes for use inpreparing the succinimide-acids of the present invention include thosepolyisobutenes that comprise at least about 20% of the more reactivemethylvinylidene isomer, preferably at least 50% and more preferably atleast 70%. Suitable polyisobutenes include those prepared using BF₃catalysts. The preparation of such polyisobutenes in which themethylvinylidene isomer comprises a high percentage of the totalcomposition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808.

[0026] Hydrocarbyl succinimides are obtained by reacting ahydrocarbyl-substitued succinic anhydride, acid, acid-ester or loweralkyl ester with an amine containing at least one primary amine group.Representative examples are given in U.S. Pat. Nos. 3,172,892;3,202,678; 3,219,666; 3,272,746; 3,254,025, 3,216,936, 4,234,435; and5,575,823. The alkenyl succinic anhydride may be prepared readily byheating a mixture of olefin and maleic anhydride to about 180-220° C.The olefin is preferably a polymer or copolymer of a lower monoolefinsuch as ethylene, propylene, isobutene and the like. The more preferredsource of alkenyl group is from polyisobutene having a molecular weightup to 5000 or higher. In a still more, preferred embodiment the alkenylis a polyisobutene group having a molecular weight of about 500-2000 andmost preferably about 700-1500.

[0027] Amines which may be reacted with the alkenyl succinic anhydrideto form the hydrocarbyl-succinimide include any that have at least oneprimary amine group that can react to form an imide group. A fewrepresentative examples are: methylamine, 2-ethylhexylamine,n-dodecylamine, stearylamine, N,N-dimethyl-propanediamine,N-(3-aminopropyl)morpholine, N-dodecyl propanediamine, N-aminopropylpiperazine ethanolamine, N-ethanol ethylene diamine and the like.Preferred amines include the alkylene polyamines such as propylenediamine, dipropylene triamine, di-(1,2butylene)-triamine,tetra-(1,2-propylene)pentaamine.

[0028] The most preferred amines are the ethylene polyamines which havethe formula H₂N(CH₂CH₂NH)_(n)H wherein n is an integer from one to ten.These ethylene polyamines include ethylene diamine, diethylene triamine,triethylene tetraamine, tetraethylene pentaamine, pentaethylenehexaamine, and the like, including mixtures thereof in which case n isthe average value of the mixture. These ethylene polyamines have aprimary amine group at each end so can form mono-alkenylsuccinimides andbis-alkenylsuccinimides. Thus especially preferred hydrocarbylsuccinimides for use in the present invention are the products ofreaction of a polyethylenepolyamine, e.g. triethylene tetramine ortetraethylene pentamine, with a hydrocarbon substituted carboxylic acidor anhydride made by reaction of a polyolefin, preferably polyisobutene,having a molecular weight of 500 to 2,000, especially 700 to 1500, withan unsaturated polycarboxylic acid or anhydride, e.g. maleic anhydride.

[0029] The Mannich base detergents of the present invention are thereaction products of an alkyl-substituted hydroxyaromatic compound,aldehydes and amines. The alkyl-substituted hydroxyaromatic compound,aldehydes and amines used in making the Mannich reaction products of thepresent invention may be any such compounds known and applied in theart, in accordance with the foregoing limitations.

[0030] Representative alkyl-substituted hydroxyaromatic compounds thatmay be used in forming the present Mannich base products arepolypropylphenol (formed by alkylating phenol with polypropylene),polybutylphenols (formed by alkylating phenol with polybutenes and/orpolyisobutylene), and polybutyl-co-polypropylphenols (formed byalkylating phenol with a copolymer of butylene and/or butylene andpropylene). Other similar long-chain alkylphenols may also be used.Examples include phenols alkylated with copolymers of butylene and/orisobutylene and/or propylene, and one or more mono-olefinic comonomerscopolymerizable therewith (e.g., ethylene, 1-pentene, 1-hexene,1-octene, 1-decene, etc.) where the copolymer molecule contains at least50% by weight, of butylene and/or isobutylene and/or propylene units.The comonomers polymerized with propylene or such butenes may bealiphatic and can also contain non-aliphatic groups, e.g., styrene,o-methylstyrene, p-methylstyrene, divinyl benzene and the like. Thus inany case the resulting polymers and copolymers used in forming thealkyl-substituted hydroxyaromatic compounds are substantially aliphatichydrocarbon polymers.

[0031] Polybutylphenol (formed by alkylating phenol with polybutylene)is preferred. Unless otherwise specified herein, the term “polybutylene”is used in a generic sense to include polymers made from “pure” or“substantially pure” 1-butene or isobutene, and polymers made frommixtures of two or all three of 1-butene, 2-butene and isobutene.Commercial grades of such polymers may also contain insignificantamounts of other olefins. So-called high reactivity polyisobuteneshaving relatively high proportions of polymer molecules having aterminal vinylidene group are also suitable for use in forming the longchain alkylated phenol reactant. Suitable high-reactivity polyisobutenesinclude those polyisobutenes that comprise at least about 20% of themore reactive methylvinylidene isomer, preferably at least 50% and morepreferably at least 70%. Suitable polyisobutenes include those preparedusing BF₃ catalysts. The preparation of such polyisobutenes in which themethylvinylidene isomer comprises a high percentage of the totalcomposition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808.

[0032] The alkylation of the hydroxyaromatic compound is typicallyperformed in the presence of an alkylating catalyst at a temperature inthe range of about 0 to about 200° C., preferably 0 to 100° C. Acidiccatalysts are generally used to promote Friedel-Crafts alkylation.Typical catalysts used in commercial production include sulphuric acid,BF₃, aluminum phenoxide, methanesulphonic acid, cationic exchange resin,acidic clays and modified zeolites.

[0033] The long chain alkyl substituents on the benzene ring of thephenolic compound are derived from polyolefin having a number averagemolecular weight (M_(n)) of from about 500 to about 3000, preferablyfrom about 500 to about 2100, as determined by gel permeationchromatography (GPC). It is also preferred that the polyolefin used havea polydispersity (weight average molecular weight/number averagemolecular weight) in the range of about 1 to about 4 (preferably fromabout 1 to about 2) as determined by GPC.

[0034] The Mannich detergent may be made from a long chain alkylphenol.However, other phenolic compounds may be used including high molecularweight alkyl-substituted derivatives of cresol, resorcinol,hydroquinone, catechol, hydroxydiphenyl, benzylphenol, phenethylphenol,naphthol, tolylnaphthol, among others. Preferred for the preparation ofthe Mannich detergents are the polyalkylphenol and polyalkylcresolreactants, e.g., polypropylphenol, polybutylphenol, polypropylcresol andpolybutylcresol, wherein the alkyl group has a number average molecularweight of about 500 to about 2100, while the most preferred alkyl groupis a polybutyl group derived from polyisobutylene having a numberaverage molecular weight in the range of about 800 to about 1300.

[0035] The preferred configuration of the alkyl-substitutedhydroxyaromatic compound is that of a para-substituted mono-alkylphenolor a para-substituted mono-alkyl ortho-cresol. However, any alkylphenolreadily reactive in the Mannich condensation reaction may be employed.Thus, Mannich products made from alkylphenols having only one ring alkylsubstituent, or two or more ring alkyl substituents are suitable for usein this invention. The long chain alkyl substituents may contain someresidual unsaturation, but in general, are substantially saturated alkylgroups.

[0036] Representative amine reactants include, but are not limited to,alkylene polyamines having at least one suitably reactive primary orsecondary amino group in the molecule. Other substituents such ashydroxyl, cyano, amido, etc., can be present in the polyamine. In apreferred embodiment, the alkylene polyamine is a polyethylenepolyamine. Suitable alkylene polyamine reactants includeethylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine and mixtures of such amines having nitrogencontents corresponding to alkylene polyamines of the formulaH₂N—(A—NH—)_(n)H, where A is divalent ethylene or propylene and n is aninteger of from 1 to 10, preferably 1 to 4. The alkylene polyamines maybe obtained by the reaction of ammonia and dihalo alkanes, such asdichloro alkanes.

[0037] In another preferred embodiment of the present invention, theamine is an aliphatic diamine having one primary or secondary aminogroup and at least one tertiary amino group in the molecule. Examples ofsuitable polyamines include N,N,N″,N″-tetraalkyldialkylenetriamines (twoterminal tertiary amino groups and one central secondary amino group),N,N,N′,N″-tetraalkyltrialkylenetetramines (one terminal tertiary aminogroup, two internal tertiary amino groups and one terminal primary aminogroup), N,N,N′,N″,N′″-pentaalkyltrialkylenetetramines (one terminaltertiary amino group, two internal tertiary amino groups and oneterminal secondary amino group), N,N-dihydroxyalkyl-alpha,omega-alkylenediamines (one terminal tertiary amino group and oneterminal primary amino group), N,N,N′-trihydroxyalkyl-alpha,omega-alkylenediamines (one terminal tertiary amino group and oneterminal secondary amino group),tris(dialkylaminoalkyl)aminoalkylmethanes (three terminal tertiary aminogroups and one terminal primary amino group), and similar compounds,wherein the alkyl groups are the same or different and typically containno more than about 12 carbon atoms each, and which preferably containfrom 1 to 4 carbon atoms each. Most preferably these alkyl groups aremethyl and/or ethyl groups. Preferred polyamine reactants areN,N-dialkyl-alpha, omega-alkylenediamine, such as those having from 3 toabout 6 carbon atoms in the alkylene group and from 1 to about 12 carbonatoms in each of the alkyl groups, which most preferably are the samebut which can be different. Most preferred isN,N-dimethyl-1,3-propanediamine and N-methyl piperazine.

[0038] Examples of polyamines having one reactive primary or secondaryamino group that can participate in the Mannich condensation reaction,and at least one sterically hindered amino group that cannot participatedirectly in the Mannich condensation reaction to any appreciable extentinclude N-(tert-butyl)-1,3-propanediamine,N-neopentyl-1,3-propanediamine,N-(tert-butyl)-1-methyl-1,2-ethanediamine,N-(tert-butyl)-1-methyl-1,3-propanediamine, and3,5-di(tert-butyl)aminoethylpiperazine.

[0039] Representative aldehydes for use in the preparation of theMannich base products include the aliphatic aldehydes such asformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde,valeraldehyde, caproaldehyde, heptaldehyde, stearaldehyde. Aromaticaldehydes which may be used include benzaldehyde and salicylaldehyde.Illustrative heterocyclic aldehydes for use herein are furfural andthiophene aldehyde, etc. Also useful are formaldehyde-producing reagentssuch as paraformaldehyde, or aqueous formaldehyde solutions such asformalin. Most preferred is formaldehyde or formalin.

[0040] The condensation reaction among the alkylphenol, the specifiedamine(s) and the aldehyde may be conducted at a temperature typically inthe range of about 40° to about 200° C. The reaction can be conducted inbulk (no diluent or solvent) or in a solvent or diluent. Water isevolved and can be removed by azeotropic distillation during the courseof the reaction. Typically, the Mannich reaction products are formed byreacting the alkyl-substituted hydroxyaromatic compound, the amine andaldehyde in the molar ratio of 1.0:0.5-2.0:1.0-3.0, respectively.

[0041] Suitable Mannich base detergents for use in the present inventioninclude those detergents taught in U.S. Pat. Nos. 4,231,759; 5,514,190;5,634,951; 5,697,988; 5,725,612; and 5,876,468, the disclosures of whichare incorporated herein by reference.

[0042] Hydrocarbyl amine detergents are known materials prepared byknown process technology. One common process involves halogenation of along chain aliphatic hydrocarbon such as a polymer of ethylene,propylene, butylene, isobutene, or copolymers such as ethylene andpropylene, butylene and isobutylene, and the like, followed by reactionof the resultant halogenated hydrocarbon with a polyamine. If desired,at least some of the product can be converted into an amine salt bytreatment with an appropriate quantity of an acid. The products formedby the halogenation route often contain a small amount of residualhalogen such as chlorine. Another way of producing suitable aliphaticpolyamines involves controlled oxidation (e.g., with air or a peroxide)of a polyolefin such as polyisobutene followed by reaction of theoxidized polyolefin with a polyamine. For synthesis details forpreparing such aliphatic polyamine detergent/dispersants, see forexample U.S. Pat. Nos. 3,438,757; 3,454,555; 3,485,601; 3,565,804;3,573,010; 3,574,576; 3,671,511; 3,746,520; 3,756,793; 3,844,958;3,852,258; 3,864,098; 3,876,704; 3,884,647; 3,898,056; 3,950,426;3,960,515; 4,022,589; 4,039,300; 4,128,403; 4,166,726; 4,168,242;5,034,471; 5,086,115; 5,112,364; and 5,124,484; and published EuropeanPatent Application 384,086. The disclosures of each of the foregoingdocuments are incorporated herein by reference. The long chainsubstituent(s) of the hydrocarbyl amine detergent most preferablycontain(s) an average of 50 to 350 carbon atoms in the form of alkyl oralkenyl groups (with or without a small residual amount of halogensubstitution). Alkenyl substituents derived from poly-alpha-olefinhomopolymers or copolymers of appropriate molecular weight (e.g.,propene homopolymers, butene homopolymers, C₃ and C₄ alpha-olefincopolymers, and the like) are suitable. Most preferably, the substituentis a polyisobutenyl group formed from polyisobutene having a numberaverage molecular weight (as determined by gel permeationchromatography) in the range of 500 to 2000, preferably 600 to 1800,most preferably 700 to 1600.

[0043] Polyetheramines suitable for use as the detergents of the presentinvention are “single molecule” additives, incorporating both amine andpolyether functionalities within the same molecule. The polyetherbackbone can be based on propylene oxide, ethylene oxide, butyleneoxide, or mixtures of these. The most preferred are propylene oxide orbutylene oxide or mixture thereof to impart good fuel solubility. Thepolyetheramines can be monoamines, diamines or triamines. Examples ofcommercially available polyetheramines are those under the tradenameJeffamines™ available from Huntsman Chemical company. The molecularweight of the polyetheramines will typically range from 500 to 3000.Other suitable polyetheramines are those compounds taught in U.S. Pat.Nos. 4,288,612; 5,089,029; and 5,112,364.

[0044] When formulating the fuel compositions of this invention, themanganese compound (with our without other additives) is employed inamounts sufficient to reduce or eliminate deposits including injectordeposits and/or control soot formation. Thus the fuels will containminor amounts of the manganese compound proportioned so as to prevent orreduce formation of engine deposits, especially fuel injector deposits.Generally speaking the fuel compositions of this invention will containan amount of manganese compound sufficient to provide from about 0.0078to about 0.25 gram of manganese per gallon of fuel, and preferably fromabout 0.0156 to about 0.125 gram of manganese per gallon.

[0045] The base fuels used in formulating the fuel compositions of thepresent invention include any base fuels suitable for use in theoperation of direct injection gasoline engines such as leaded orunleaded motor gasolines, and so-called reformulated gasolines whichtypically contain both hydrocarbons of the gasoline boiling range andfuel-soluble oxygenated blending agents (“oxygenates”), such asalcohols, ethers and other suitable oxygen-containing organic compounds.Preferably, the fuel is a mixture of hydrocarbons boiling in thegasoline boiling range. This fuel may consist of straight chain orbranch chain paraffins, cycloparaffins, olefins, aromatic hydrocarbonsor any mixture of these. The gasoline can be derived from straight runnaptha, polymer gasoline, natural gasoline or from catalyticallyreformed stocks boiling in the range from about 80° to about 450° F. Theoctane level of the gasoline is not critical and any conventionalgasoline may be employed in the practice of this invention.

[0046] Oxygenates suitable for use in the present invention includemethanol, ethanol, isopropanol, t-butanol, mixed C1 to C5 alcohols,methyl tertiary butyl ether, tertiary amyl methyl ether, ethyl tertiarybutyl ether and mixed ethers. Oxygenates, when used, will normally bepresent in the base fuel in an amount below about 30% by volume, andpreferably in an amount that provides an oxygen content in the overallfuel in the range of about 0.5 to about 5 percent by volume.

[0047] In a preferred embodiment, the detergents are preferably usedwith a liquid carrier or induction aid. Such carriers can be of varioustypes, such as for example liquid poly-α-olefin oligomers, mineral oils,liquid poly(oxyalkylene) compounds, liquid alcohols or polyols,polyalkenes, liquid esters, and similar liquid carriers. Mixtures of twoor more such carriers can be employed.

[0048] Preferred liquid carriers include 1) a mineral oil or a blend ofmineral oils that have a viscosity index of less than about 120, 2) oneor more poly-α-olefin oligomers, 3) one or more poly(oxyalkylene)compounds having an average molecular weight in the range of about 500to about 3000, 4) polyalkenes, 5) polyalkyl-substituted hydroxyaromaticcompounds or 6) mixtures thereof. The mineral oil carrier fluids thatcan be used include paraffinic, naphthenic and asphaltic oils, and canbe derived from various petroleum crude oils and processed in anysuitable manner. For example, the mineral oils may be solvent extractedor hydrotreated oils. Reclaimed mineral oils can also be used.Hydrotreated oils are the most preferred. Preferably the mineral oilused has a viscosity at 40° C. of less than about 1600 SUS, and morepreferably between about 300 and 1500 SUS at 40° C. Paraffinic mineraloils most preferably have viscosities at 40° C. in the range of about475 SUS to about 700 SUS. For best results, it is highly desirable thatthe mineral oil have a viscosity index of less than about 100, morepreferably, less than about 70 and most preferably in the range of fromabout 30 to about 60.

[0049] The poly-α-olefins (PAO) suitable for use as carrier fluids arethe hydrotreated and unhydrotreated poly-α-olefin oligomers, i.e.,hydrogenated or unhydrogenated products, primarily trimers, tetramersand pentamers of α-olefin monomers, which monomers contain from 6 to 12,generally 8 to 12 and most preferably about 10 carbon atoms. Theirsynthesis is outlined in Hydrocarbon Processing, February 1982, page 75et seq., and in U.S. Pat. Nos. 3,763,244; 3,780,128; 4,172,855;4,218,330; and 4,950,822. The usual process essentially comprisescatalytic oligomerization of short chain linear alpha olefins (suitablyobtained by catalytic treatment of ethylene). The poly-α-olefins used ascarriers will usually have a viscosity (measured at 100° C.) in therange of 2 to 20 centistokes (cSt). Preferably, the poly-α-olefin has aviscosity of at least 8 cSt, and most preferably about 10 cSt at 100° C.

[0050] The poly (oxyalkylene) compounds which are among the preferredcarrier fluids for use in this invention are fuel-soluble compoundswhich can be represented by the following formula

R₁—(R₂—O)_(n)—R₃

[0051] wherein R₁ is typically a hydrogen, alkoxy, cycloalkoxy, hydroxy,amino, hydrocarbyl (e.g., alkyl, cycloalkyl, aryl, alkylaryl, aralkyl,etc.), amino-substituted hydrocarbyl, or hydroxy-substituted hydrocarbylgroup, R₂ is an alkylene group having 2-10 carbon atoms (preferably 2-4carbon atoms), R₃ is typically a hydrogen, alkoxy, cycloalkoxy, hydroxy,amino, hydrocarbyl (e.g., alkyl, cycloalkyl, aryl, alkylaryl, aralkyl,etc.), amino-substituted hydrocarbyl, or hydroxy-substituted hydrocarbylgroup, and n is an integer from 1 to 500 and preferably in the range offrom 3 to 120 representing the number (usually an average number) ofrepeating alkyleneoxy groups. In compounds having multiple —R₂—O—groups, R₂ can be the same or different alkylene group and wheredifferent, can be arranged randomly or in blocks. Preferred poly(oxyalkylene) compounds are monools comprised of repeating units formedby reacting an alcohol with one or more alkylene oxides, preferably onealkylene oxide, more preferably propylene oxide or butylene oxide.

[0052] The average molecular weight of the poly (oxyalkylene) compoundsused as carrier fluids is preferably in the range of from about 500 toabout 3000, more preferably from about 750 to about 2500, and mostpreferably from above about 1000 to about 2000.

[0053] One useful sub-group of poly (oxyalkylene) compounds is comprisedof the hydrocarbyl-terminated poly(oxyalkylene) monools such as arereferred to in the passage at column 6, line 20 to column 7 line 14 ofU.S. Pat. No. 4,877,416 and references cited in that passage, saidpassage and said references being fully incorporated herein byreference.

[0054] A preferred sub-group of poly (oxyalkylene) compounds iscomprised of one or a mixture of alkylpoly (oxyalkylene)monools which inits undiluted state is a gasoline-soluble liquid having a viscosity ofat least about 70 centistokes (cSt) at 40° C. and at least about 13 cStat 100° C. Of these compounds, monools formed by propoxylation of one ora mixture of alkanols having at least about 8 carbon atoms, and morepreferably in the range of about 10 to about 18 carbon atoms, areparticularly preferred.

[0055] The poly (oxyalkylene) carriers used in the practice of thisinvention preferably have viscosities in their undiluted state of atleast about 60 cSt at 40° C. (more preferably at least about 70 cSt at40° C.) and at least about 11 cSt at 100° C. (more preferably at leastabout 13 cSt at 100° C.). In addition, the poly (oxyalkylene) compoundsused in the practice of this invention preferably have viscosities intheir undiluted state of no more than about 400 cSt at 40° C. and nomore than about 50 cSt at 100° C. More preferably, their viscositieswill not exceed about 300 cSt at 40° C. and will not exceed about 40 cStat 100° C.

[0056] Preferred poly (oxyalkylene) compounds also include poly(oxyalkylene) glycol compounds and monoether derivatives thereof thatsatisfy the above viscosity requirements and that are comprised ofrepeating units formed by reacting an alcohol or polyalcohol with analkylene oxide, such as propylene oxide and/or butylene oxide with orwithout use of ethylene oxide, and especially products in which at least80 mole % of the oxyalkylene groups in the molecule are derived from1,2-propylene oxide. Details concerning preparation of suchpoly(oxyalkylene) compounds are referred to, for example, inKirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, Volume18, pages 633-645 (Copyright 1982 by John Wiley & Sons), and inreferences cited therein, the foregoing excerpt of the Kirk-Othmerencyclopedia and the references cited therein being incorporated hereinin toto by reference. U.S. Pat. Nos. 2,425,755; 2,425,845; 2,448,664;and 2,457,139 also describe such procedures, and are fully incorporatedherein by reference.

[0057] The poly (oxyalkylene) compounds, when used, pursuant to thisinvention will contain a sufficient number of branched oxyalkylene units(e.g., methyldimethyleneoxy units and/or ethyldimethyleneoxy units) torender the poly (oxyalkylene) compound gasoline soluble.

[0058] Suitable poly (oxyalkylene) compounds for use in the presentinvention include those taught in U.S. Pat. Nos. 5,514,190; 5,634,951;5,697,988; 5,725,612; 5,814,111 and 5,873,917, the disclosures of whichare incorporated herein by reference.

[0059] The polyalkenes suitable for use as carrier fluids in the presentinvention include polypropene and polybutene. The polyalkenes of thepresent invention preferably have a molecular weight distribution(Mw/Mn) of less than 4. In a preferred embodiment, the polyalkenes havea MWD of 1.4 or below. Preferred polybutenes have a number averagemolecular weight (Mn) of from about 500 to about 2000, preferably 600 toabout 1000, as determined by gel permeation chromatography (GPC).Suitable polyalkenes for use in the present invention are taught inco-pending US application 09/201,113 filed Nov. 30, 1998.

[0060] The polyalkyl-substituted hydroxyaromatic compounds suitable foruse as carrier fluid in the present invention include those compoundsknown in the art as taught in U.S. Pat. Nos. 3,849,085; 4,231,759;4,238,628; 5,300,701; 5,755,835 and 5,873,917, the disclosures of whichare incorporated herein by reference.

[0061] When the carrier fluids are used in combination with the aminedetergents, the ratio (wt/wt) of detergent to carrier fluid(s) istypically in the range of from 1:0.1 to 1:3.

[0062] The additives used in formulating the preferred fuels of thepresent invention can be blended into the base fuel individually or invarious sub-combinations. However, it is preferable to blend all of thecomponents concurrently using an additive concentrate as this takesadvantage of the mutual compatibility afforded by the combination ofingredients when in the form of an additive concentrate. Also use of aconcentrate reduces blending time and lessens the possibility ofblending errors.

[0063] A preferred embodiment of the present invention comprises amethod for controlling injector deposits in a direct injection gasolineengine which comprises introducing into a direct injection gasolineengine with the combustion intake charge a spark-ignition fuelcomposition comprising a) a spark-ignition fuel and b) a fuel-solublecyclopentadienyl manganese tricarbonyl compound.

[0064] Another preferred embodiment of the present invention comprises amethod for reducing soot loading in the crankcase lubricating oil of avehicle having a direct injection gasoline engine which comprisesintroducing into a direct injection gasoline engine with the combustionintake charge a spark-ignition fuel composition comprising a) aspark-ignition fuel and b) a fuel-soluble cyclopentadienyl manganesetricarbonyl compound.

EXAMPLES

[0065] The practice and advantages of this invention are demonstrated bythe following examples which are presented for purposes of illustrationand not limitation.

[0066] The manganese compound used in the following examples wasmethylcyclopentadienyl manganese tricarbonyl (MMT).

[0067] The Mannich detergents used in the following examples werederived by reaction of a long chain alkylated phenol (“PBP”),N,N-dimethyl-1,3-propanediamine (“DMPD”), and formaldehyde (“FA”). ThePBP was formed by reacting phenol with a polyisobutylene having analkylvinylidene isomer content of less than 10% and a number averagemolecular weight of about 900.

[0068] To demonstrate the effectiveness of the additive systems of thepresent invention in reducing deposits in direct injection gasolineengines, tests were conducted in a 1982 Nissan Z22e (2.2 liter)dual-sparkplug, four-cylinder engine modified to run in a homogeneousdirect injection mode, at a fuel rich lambda of 0.8 to accelerateinjector deposit formation. Details of this test are set forth in Aradi,A. A., Imoehl, B., Avery, N. L., Wells, P. P., and Grosser, R. W.: “TheEffect of Fuel Composition and Engine Operating Parameters on InjectorDeposits in a High-Pressure Direct Injection Gasoline (DIG) ResearchEngine”, SAE Technical Paper 1999-01-3690 (1999).

[0069] Modifications to the engine included replacing the exhaust-sidespark plugs with pre-production high-pressure common rail directinjectors, removing the OEM spark and fuel system, and installing ahigh-pressure fuel system and universal engine controller. Table 1summarizes the specifications of the modified test engine. Forhomogeneous combustion, flat-top pistons and the conventional gasolinespark ignition combustion chamber design were found to be sufficient forthis type of research work. The injectors were located on the hot (i.e.exhaust) side of the engine to favor high tip temperatures to promoteinjector deposit.

[0070] The rate of injector deposit formation was evaluated through theuse of this specially developed steady-state engine test. Engineoperating conditions for each test point were determined by mappinginjector tip temperatures throughout the engine operating map range. Theinjectors were modified with thermocouples at the tip. Key parameterswere inlet air and fuel temperatures, engine speed, and engine load. Theinlet air and fuel temperatures were subsequently controlled at 35° C.and 32° C., respectively. TABLE 1 Test Engine Specifications FourCylinder In-Line 2.2 L Nissan Type Engine Converted for DI OperationDisplacement 2187 cubic centimeters Plugs/cylinder 1 (stockconfiguration: 2) Valves/cylinder 2 Bore 87 millimeters Stroke 92millimeters Fuel System Common Rail High Pressure Direct Injection FuelPressure 6900 kPa (closed loop) Engine Controller Universal LaboratorySystem Injection Timing 300 degrees BTDC Coolant Temperature (° C.) 85Oil Temperature (° C.) 95

[0071] At constant inlet air/fuel temperature and engine load, tiptemperature remained constant at engine speeds of 1500, 2000, 2500, and3000 rpm. However, at constant engine speed, tip temperatures increasewith load. For five load points, 200, 300, 400, 500, and 600 mg/strokeair charge, increasing tip temperatures of 120, 140, 157, 173, and 184°C., respectively, were observed for each load.

[0072] Through previous research, it was determined that a tiptemperature of 173° C. provided optimum conditions for injector depositformation in this engine. Table 2 sets forth the key test conditionsused in performing the evaluation of the additives of the presentinvention. TABLE 2 Key Test Conditions Engine Speed (rpm) 2500 Inlet AirTemp. (° C.) 35 Inlet Fuel Temp. (° C.) 32 Exit Coolant Temp. (° C.) 85Exit Oil Temp. (° C.) 95 Load (mg air/stroke) 500 Injector Tip Temp. (°C.) 173

[0073] The test was divided into three periods: engine warm-up, anoperator-assisted period, and test period. Engine speed was controlledusing the engine dynamometer controller, and the engine throttle wasmanipulated to control air charge using a standard automotive airflowmeter as feedback in a closed-loop control system. Engine fueling wascontrolled in two ways. During warm-up, injector pulse width wascontrolled using a standard mass airflow strategy and exhaust gas sensorcontrolling the air/fuel mixture to stoichiometric. During the operatorinteraction period, the pulse width was manually set for each injectorusing wide-range lambda sensors in the exhaust port of each cylinder.Fuel flow was measured using a volumetric flow meter and atemperature-corrected density value was used to calculate mass flow.

[0074] Each fuel was run at a load condition of 500 mg/stroke. Injectordeposit formation was followed by measuring total engine fuel flow atfixed speed, air charge (mass of air per intake stroke), and the lambdasignal from each cylinder over a test period of six hours.

[0075] To help minimize injector-to-injector variability the same set ofinjectors was used for all tests at a particular engine load, with eachinjector always in the same cylinder.

[0076] Gasoline fuel compositions were subjected to the above-describedengine tests whereby the substantial effectiveness of these compositionsin minimizing injector deposit formation was conclusively demonstrated.The fuel used for these tests was a Howell EEE fuel having a T₉₀ (° C.)of 160, an olefin content of 1.2% and a sulfur content of 20 ppm. Thedetergent additives used and the percent flow loss for the fuels at tiptemperatures of 173° C. are set forth in Table 3. TABLE 3 Percent flowloss Sample MMT # (g Mn/gallon) Detergent (ptb) Flow loss (%) 1* None —10.24 2 1/64 — 5.37 3 1/32 — 6.26 4* None Mannich¹ (60) 4.33 5 1/64Mannich¹ (60) 4.16 6 1/32 Mannich¹ (60) 2.91

[0077] It is clear from examination of Table 3 that the addition ofmanganese compounds to fuels for use in direct injection gasolineengines provides unexpected improvements (reductions) in injectordeposits when added to the base fuel as well as improving theeffectiveness of a detergent in reducing injector deposits.

[0078] It is to be understood that the reactants and components referredto by chemical name anywhere in the specification or claims hereof,whether referred to in the singular or plural, are identified as theyexist prior to coming into contact with another substance referred to bychemical name or chemical type (e.g., base fuel, solvent, etc.). Itmatters not what chemical changes, transformations and/or reactions, ifany, take place in the resulting mixture or solution or reaction mediumas such changes, transformations and/or reactions are the natural resultof bringing the specified reactants and/or components together under theconditions called for pursuant to this disclosure. Thus the reactantsand components are identified as ingredients to be brought togethereither in performing a desired chemical reaction (such as a Mannichcondensation reaction) or in forming a desired composition (such as anadditive concentrate or additized fuel blend). It will also berecognized that the additive components can be added or blended into orwith the base fuels individually per se and/or as components used informing preformed additive combinations and/or sub-combinations.Accordingly, even though the claims hereinafter may refer to substances,components and/or ingredients in the present tense (“comprises”, “is”,etc.), the reference is to the substance, components or ingredient as itexisted at the time just before it was first blended or mixed with oneor more other substances, components and/or ingredients in accordancewith the present disclosure. The fact that the substance, components oringredient may have lost its original identity through a chemicalreaction or transformation during the course of such blending or mixingoperations is thus wholly immaterial for an accurate understanding andappreciation of this disclosure and the claims thereof.

[0079] As used herein the term “fuel-soluble” or “gasoline-soluble”means that the substance under discussion should be sufficiently solubleat 20° C. in the base fuel selected for use to reach at least theminimum concentration required to enable the substance to serve itsintended function. Preferably, the substance will have a substantiallygreater solubility in the base fuel than this. However, the substanceneed not dissolve in the base fuel in all proportions.

[0080] At numerous places throughout this specification, reference hasbeen made to a number of U.S. Patents and published foreign patentapplications. All such cited documents are expressly incorporated infull into this disclosure as if fully set forth herein.

[0081] This invention is susceptible to considerable variation in itspractice. Therefore the foregoing description is not intended to limit,and should not be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

We claim:
 1. A method for controlling injector deposits in a directinjection gasoline engine which comprises introducing into a directinjection gasoline engine with the combustion intake charge aspark-ignition fuel composition comprising a) a spark-ignition fuel andb) a fuel-soluble cyclopentadienyl manganese tricarbonyl compound. 2.The method of claim 1 wherein the spark-ignition fuel compositioncomprises the fuel-soluble cyclopentadienyl manganese tricarbonylcompound in proportions effective to reduce the volume of injectordeposits in a direct injection gasoline engine operated on aspark-ignition fuel containing an injector deposit-controlling amount ofsaid fuel-soluble cyclopentadienyl manganese tricarbonyl compound tobelow the volume of injector deposits in said direct injection gasolineengine operated in the same manner on the same spark-ignition fuelexcept that it is devoid of a fuel-soluble cyclopentadienyl manganesetricarbonyl compound.
 3. The method of claim 1 wherein thespark-ignition fuel comprises gasoline.
 4. The method of claim 1 whereinthe spark-ignition fuel comprises a blend of hydrocarbons of thegasoline boiling range and a fuel-soluble oxygenated compound.
 5. Themethod of claim 1 wherein said cyclopentadienyl manganese tricarbonylcompound comprises at least one member selected from the groupconsisting of cyclopentadienyl manganese tricarbonyl,methylcyclopentadienyl manganese tricarbonyl and mixtures thereof. 6.The method of claim 1 wherein the fuel-soluble cyclopentadienylmanganese tricarbonyl compound is present in an amount sufficient toprovide 0.0078 to 0.25 gram of manganese per gallon of fuel.
 7. Themethod of claim 6 wherein the fuel-soluble cyclopentadienyl manganesetricarbonyl compound is present in an amount sufficient to provide0.0156 to 0.125 gram of manganese per gallon of fuel.
 8. The method ofclaim 1 wherein the fuel composition further comprises at least oneamine detergent.
 9. The method of claim 8 wherein the amine detergentcomprises at least one member selected from the group consisting ofhydrocarbyl-substituted succinic anhydride derivatives, Mannichcondensation products, hydrocarbyl amines and polyetheramines.
 10. Themethod of claim 9 wherein the hydrocarbyl-substituted succinic anhydridederivatives comprise at least one member selected from the groupconsisting of hydrocarbyl succinimides, hydrocarbyl succinamides,hydrocarbyl succinimide-amides and hydrocarbyl succinimide-esters. 11.The method of claim 1 wherein the fuel composition further comprises acarrier fluid selected from the group consisting of 1) a mineral oil ora blend of mineral oils that have a viscosity index of less than about120, 2) one or more poly-α-olefin oligomers, 3) one or more poly(oxyalkylene) compounds having an average molecular weight in the rangeof about 500 to about 3000, 4) one or more polyalkenes, 5) one or morepolyalkyl-substituted hydroxyaromatic compounds and 6) mixtures thereof.12. The method of claim 11 wherein the carrier fluid comprises at leastone poly (oxyalkylene) compound.
 13. The method of claim 1 wherein thefuel composition further comprises at least one additive selected fromthe group consisting of antioxidants, carrier fluids, metaldeactivators, dyes, markers, corrosion inhibitors, biocides, antistaticadditives, drag reducing agents, demulsifiers, dehazers, anti-icingadditives, antiknock additives, anti-valve-seat recession additives,lubricity additives and combustion improvers.
 14. A method for reducingsoot loading in the crankcase lubricating oil of a vehicle having adirect injection gasoline engine which comprises introducing into adirect injection gasoline engine with the combustion intake charge aspark-ignition fuel composition comprising a) a spark-ignition fuel andb) a fuel-soluble cyclopentadienyl manganese tricarbonyl compound. 15.The method of claim 14 wherein the spark-ignition fuel compositioncomprises the fuel-soluble cyclopentadienyl manganese tricarbonylcompound in proportions effective to reduce the amount of soot loadingin the crankcase lubricating oil to below the amount of soot loading insaid crankcase lubricating oil when said vehicle is operated in the samemanner and on the same spark-ignition fuel except that the fuel isdevoid of a fuel-soluble cyclopentadienyl manganese tricarbonylcompound.
 16. The method of claim 14 wherein the spark-ignition fuelcomprises gasoline.
 17. The method of claim 14 wherein thespark-ignition fuel comprises a blend of hydrocarbons of the gasolineboiling range and a fuel-soluble oxygenated compound.
 18. The method ofclaim 14 wherein said cyclopentadienyl manganese tricarbonyl compoundcomprises at least one member selected from the group consisting ofcyclopentadienyl manganese tricarbonyl, methylcyclopentadienyl manganesetricarbonyl and mixtures thereof.
 19. The method of claim 14 wherein thefuel-soluble cyclopentadienyl manganese tricarbonyl compound is presentin an amount sufficient to provide 0.0078 to 0.25 gram of manganese pergallon of fuel.
 20. The method of claim 19 wherein the fuel-solublecyclopentadienyl manganese tricarbonyl compound is present in an amountsufficient to provide 0.0156 to 0.125 gram of manganese per gallon offuel.
 21. The method of claim 14 wherein the fuel composition furthercomprises at least one amine detergent.
 22. The method of claim 21wherein the amine detergent comprises at least one member selected fromthe group consisting of hydrocarbyl-substituted succinic anhydridederivatives, Mannich condensation products, hydrocarbyl amines andpolyetheramines.
 23. The method of claim 22 wherein thehydrocarbyl-substituted succinic anhydride derivatives comprise at leastone member selected from the group consisting of hydrocarbylsuccinimides, hydrocarbyl succinamides, hydrocarbyl succinimide-amidesand hydrocarbyl succinimide-esters.
 24. The method of claim 14 whereinthe fuel composition further comprises a carrier fluid selected from thegroup consisting of 1) a mineral oil or a blend of mineral oils thathave a viscosity index of less than about 120, 2) one or morepoly-α-olefin oligomers, 3) one or more poly (oxyalkylene) compoundshaving an average molecular weight in the range of about 500 to about3000, 4) one or more polyalkenes, 5) one or more polyalkyl-substitutedhydroxyaromatic compounds and 6) mixtures thereof.
 25. The method ofclaim 14 wherein the carrier fluid comprises at least one poly(oxyalkylene) compound.
 26. The method of claim 14 wherein the fuelcomposition further comprises at least one additive selected from thegroup consisting of antioxidants, carrier fluids, metal deactivators,dyes, markers, corrosion inhibitors, biocides, antistatic additives,drag reducing agents, demulsifiers, dehazers, anti-icing additives,antiknock additives, anti-valve-seat recession additives, lubricityadditives and combustion improvers.